List of Footnotes

1 The star claimed to be “the closest ever solar twin” (Porto de Mello and da Silva, 1997), HR 6060, shows parameters nearly indistinguishable from solar values indeed: L∕L⊙ = 1.05 ± 0.02; spectral type G2 Va (Sun: G2 V); BV = 0.65 (Sun: 0.648); UB = 0.17 (Sun: 0.178); Teff = 5789 K (Sun: 5777 K; ΔTeff = 12 ± 30 K); log g = 4.49 (Sun: 4.44; Δ log g = 0.05 ± 0.12), microturbulence velocity ξ = 1.54 km s–1 (Sun: 1.52 km s–1; Δ ξ = [0.02 ± 0.04] km s–1); element abundances solar within 1σ, in particular [Fe/H] = 0.05 ± 0.06; Mount Wilson activity index < S > = 0.174 (Sun: 0.177 in 1980); rotational velocity v sin i < 3.0 km s–1 (Sun: v = 2 km s–1).
2 The line fluxes of O viii, O vii, N vii, and C vi were determined from a model spectrum synthesized in the XSPEC software (Arnaud, 1996) using the vapec model (Smith et al., 2001). The model is based on an isothermal plasma with a temperature of 2 MK normalized such that the 0.1 – 10 keV luminosity is 2 × 1027 erg s–1. The low-FIP element abundances were set to values four times higher than standard photospheric abundances, while the high-FIP element abundances were photospheric; the S abundance was set to an intermediate value of 2 × the photospheric value.
3 Meyer normalized the abundances such that the low-FIP element abundances were photospheric and the high-FIP abundances depleted, whereas the present-day view is that high-FIP elements are at photospheric levels, see Feldman (1992).